Vehicles of the type involved herein are classified in class 214, subclass 82 et seq. For relevant prior art, see U.S. Pat. Nos. 3,796,330 and 4,004,703. The vehicles disclosed in said patents suffer from one or more of the following disadvantages.
To ensure a vertical disposition and provide parallel guidance of the pushing means in said patents, synchronized chains or ropes are employed, which results in a very expensive and difficult to maintain arrangement. In U.S. Pat. No. 3,796,330, the arrangement creates a considerable reduction of cargo space which results in a loss of payload. Due to a moment arm affect wherein the prior pushing means tends to rotate about vertical axes, lateral connecting beams are provided to resist such rotation. One of said connecting beams is adjacent the floor and lift trucks must pass over the same when loading the vehicle.
The prior art vehicles due to their construction have control problems due to said wall bulge. It is difficult to have access to cables, chains and the like for maintenance purposes. The side walls of the vehicles have projections which rub against the compressible product thereby damaging the same. These and other disadvantages of the prior art are overcome by the present invention.
The structural strength of conventional, standard dry cargo semi-trailers is not sufficient to withstand the loads imposed upon them by these loading systems. Consequently, specially engineered and constructed trailers must be used, resulting in a much higher cost. In other words, these loading systems cannot be economically added to standard construction semi-trailers.
The system described in U.S. Pat. No. 4,004,703 has one major drawback. The "pushing means" (or, in this case, it would actually be "pulling means") have no mechanical, built-in provision for returning to the open (rear) end of the trailer enclosure to receive the next load and to perform another loading (compression) cycle. The "pull cables" must be returned to the rear by hand (impossible due to the resisting forces involved) or by some mechanical device such as forklift truck dragging them out. The basic problem, of course, is that the actuating mechanism, block-and-tackle, is a "one way motion" device. It can pull ropes or cables, but it cannot push them back.